Transducer element



Oct. 4, 1960 w. T. HARRIS TRANSDUCER ELEMENT Filed March 6, 1957 B \\QNsw QN R KNJ, N R m n E I TI N X I I, I, NRU 1/ VU w W W i Y B PatentedOct. 4, 1960 TRANSDUCER ELEMENT Wilbur T. Harris, Southbury, Conm,assignor to The Harris Transducer Corporation, Woodbury, Conn., acorporation of Connecticut Filed Mar. 6, 1957, Ser. No. 644,289

21 Claims. (Cl. 310-26) My invention relates to an improved transducerconstruction and to a method of producing the same. This inventionincorporates certain improvements over my copending application SerialNo. 475,462, filed December 15, 1954, and is related to my applicationSerial No. 558,947, filed January 13, 1956. This application is acontinuation-impart of my copending application, Serial No. 559,657,filed January 17, 1956, now abandoned.

It is an object of the invention to provide an improved construction andmethod of the character indicated.

It is another object to provide a new transducer construction featuringimportant economies in the use of magnetostrictive materials withoutsacrificing efiiciency of performance.

It is another object to provide an improved transducer construction inwhich important reductions in quantities of magnetostrictive metal scrapmay be realized.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

Fig. 1 is a simplified view in perspective and partly broken away toreveal apparatus for carrying out part of my improved method oftransducer construction;

Fig. 2 is a perspective view of a completed transducer element of myinvention;

Fig. 3 is a sectional view in the plane 3-3 of Fig. 2; and

Fig. 4 is a sectional view similar to Fig. 3, but showing amodification.

Briefly stated, my invention contemplates an improved transducerconstruction in which magnetostrictive material is employed essentiallyonly in that part of the magnetic circuit which is relied upon formagnetostrictive elongation and contraction. Thus, the basic core may bemerely an elongated fork having spaced arms or legs bonded at one end byan integral yoke, and the magnetic circuit may be completed by apermanently magnetized ferrite block. Electrical coupling is developedto the legs, and counterweight end masses are separately fabricated andbonded to the longitudinal ends of the stack of laminations. The endcounterweights are preferably precision-cast, with recesses conformingto the crosssection of the end of the magnetostrictive core received.therein; for a laminated core, these recesses thus serve a jiggingfunction, and whether the core is cast or laminated, these recesses helpto provide extended-surface contact for firmly bonding thecounterweights to the core.

In my method of producing the laminated-core embodiment of my invention,a new lamination is sheared from a continuous'strip of magnetostrictivemetal, for each press cycle; The individual laminations are collectedand automatically .stacked in a parting-agent bath located directlybeneath the newly cut-01f piece. An automatic counting mechanismdetermines when the full stack has been accumulated and may serve toshut off the shearing operation until the stack has been removed and anew stacking jig placed beneath the cut-01f location. The stackcollected in the parting-agent bath is removed as a whole and placed inan annealing oven in an inert or reducing atmosphere and is thereafterchemically or otherwise treated in order that the laminations may havesome measure of insulation inherent in their surfaces. The stack is thencompressed and bonded in a consolidating operation.

Referring to Figs. 2 and 3 of the drawings, my invention is shown inapplication to an elongated transducer element comprising a stackedplurality of like laminations 10. Each lamination comprises laterallyspaced elongated legs 11-12 integrally joined at a yoke end 13. Apermanent-magnet ferrite block 14 spaces the free ends of the legs 11-12and is bonded thereto; preferably, the block 14 is bonded at a locationjust short of the longitudinal ends of legs 11-12 so that these endsproject beyond block 14. A head counterweight 15 and a tailcounterweight 16 are each suitably recessed to receive the respectiveends of the consolidated stack; the weights 15-16 are preferably ofnon-magnetic material, thereby avoiding shunting effects, A.C. fluxpentration and eddy-current losses therein.

In the form shown, the head counterweight 15 receives the yoke end 13 ofthe stack at its recess 17; the head 15 is preferably of a materialcomprising essentially aluminum so as to be relatively light in weight.The head 15 is preferably precision-cast, and the recess 17 conformsclosely to the cross section of the yoke end 13 so as to perform aself-jigging function when receiving the stacked laminations, therebypermitting establishment of a good bond to the stack. In like manner,the tail weight 16 is recessed at 18-19 to accommodate the projectingends of the lamination legs 11-12, and the tail 16 is also preferablyprecision-cast so as closely to receive the legs 11-12 and to permitsecure bonding; the tail weight 16 is relatively substantially heavierthan the head weight 15 and is preferably of a zinc-alloy construction.Winding means 20 is linked to the magnetic circuit defined by legs11-12-13 and by block 14, and in the form shown, separate windings oflike numbered turns are linked to each of the legs 11-12. The

windings 20-20 may be developed separately on forms having the crosssection of the legs 11-12 and merely insertably applied to the legs11-12 before the ferrite block 14 is bonded thereto.

In use, the element of Fig. 2 may form part of an array of similarelements, in side-by-side relation, with sets of legs 11-12 of adjacentelements either parallel to each other or slightly inclined (as whenorienting the individual elements about a central support, from whichthe heads 15 project radially outwardly). In such an array, asound-transparent boot or diaphragm would cover all heads. As far aseach array element is concerned, endfor-end symmetrical loading is notnecessary and is not intended; thus, the head weight 15 is preferablylighter than the tail weight 16, even when the radiation load is addedto the head weight 15. With such proportioning, i.e., if the head 15,with its radiation load, is lighter than the tail 16, then higherdisplacement amplitude and greater radiation resistance may be realized.

In the mass production of laminations of the character indicated, Iprefer to employ a two-stage process, which may involve a single powerpress operating on a continuous strip 21 of magnetostrictive metal. At afirst stage, a rectangular punch 22 and a small central circular punch23 develop openings 24-25 in the strip, thus defining the spacedstretches which ultimately become the legs 11-12 and also defining at 25a hole in the yoke 13 for locating purposes. The power press may alsocarry a shear member 26 spaced by one lamination length from the punchelements 22-23, so that when in a second location indexed by onelamination length (or by an integer multiple of lamination lengths) fromthe punch location, the locating hole 25 is poised to receive an elementof indexing mechanism 28-29. In Fig. 1, I identify this location of thehole 25 by the designation 25.

The indexing mechanism is shown schematically to comprise longitudinallyreciprocating means including feed elements 38-29; the indexing meanswill be understood to incorporate means (not shown) for feeding onelamination length (or an integer multiple thereof) for each cycle ofoperation. Means (not shown) and either responsive to the indexing means28-29 or to: movement of some other recycling part of the press mayengage the trip of counting mechanism 32 to determine when a de sirednumber of laminations has been out off. T he counter is shown to includean adjustable knob 33 for preselecting the number of laminations to becut in a given stack, and at 34 I suggest that, upon determination thatthe preselected number of laminations has been cut, a control functionwill be developed to temporarily shut off the production of furtherlaminations.

In Fig. l, the showing of tool elements and indexing mechanism is purelyschematic, and it will suffice merely to describe the succession ofevents. As a first step, the punches 22-23 descend to punch out theholes iii-25. In the same reciprocation of the head of the power press,but with preferably slightly delayed action (due to use of a blade 26which is shorter than other punch elements 22-23), the shear 26 descendsto cut off a new lamination The new lamination 10 drops off and thepress head is withdrawn to permit indexing. The cycle then repeats.

In accordance with my invention, I provide for auto matically stackingthe newly formed laminations 10 in slightly spaced relation so as tofacilitate subsequent heat treatment and surface-insulation treatmentprior to consolidation. In the form shown, this is achieved in a bath 35containing an aqueous suspension of parting agent, such as talc or milkof magnesia. Recirculating mechanism. including a pump 36 assurescontinuous uniform suspension of the parting agent in the bath 35. A jig37 may be seated on the bottom of bath 35 and may include an upstandinglocating pin 38 poised to intercept the hole 25 of a newly cut offlamination as it begins to fall. I prefer that the upper end of thelocating pin 38 shall be tapered so as to minimize the risk of foulingand so as to provide least possible friction to the free fall of eachnew lamination; this tapering preferably ends at or below the surface ofthe parting-agent fluid. Further accuracy of location may be achieved byemploying a second pin 3% to locate between the free ends of the legs11-12.

After the counting means 32 has determined that a stack of desired sizehas been accumulated on the jig 37, the production of furtherlaminations is temporarily stopped so as to permit bodily removal of thejig 37 with its accumulated stack of laminations. The parting agent hasassured adequate, though small, spacing between adjacent laminations sothat the jig and stack may be placed as a unit in an annealing oven.Preferably, this is a conveyorized device and annealing takes place in areducing atmosphere, such as a mixture of hydrogen and nitrogen. Afterannealing, the individual laminations are surface-treated to provide anoxidized film or surface for better electrical insulation betweenlaminations. The chemical mechanism for performing this function is wellknown, and a black oxide may be readily developed on nickel laminationswithout requiring any further physical separation between laminationsthan that provided by the parting agent.

After surface-treating the annealed stack, the batch of laminations isclamped in a jig, with the yoke end 13 fitted into the cavity 17 of thehead 15. Before fitting in this manner, the cavity 17 is first linedwith a solventfree typebonding ,agent (e.g. an epoxy resin), and theyoke end is bonded to the head 15 in a first curing operation, which maybe performed in a conveyorized lowtemperature oven. The transducerelement is thereafter finished by applying windings 20-21 of insulatedwire, by insertion of the magnet 14-, and by placement of the tailcounterweight 16. In the latter step, bonding may be accomplished againin a conveyorized oven, using a suit-able bonding agent as described inconnection with bonding at the head end.

In Fig. 4, I show a modification in which the basic core 423 is ofmagnetostrictive ceramic, cast as a single piece into the generallyforked shape shown, thereby defining a yoke portion 41 integrallyjoining two spaced elongated leg portions 42-43; the core ceramic ispreferably of magnetically soft material (ie not permanentrnagnetmaterial), such as pure nickel ferrite (NiFe O A permanent-magnet insert44, which may also be of ferrite (as, for example, barium ferrite (BaFeOQ completes the flux path, and for efiicienc winding means 20-20 isdeveloped along both legs 42-43. Head and tail weights of theproportions discussed at 15-16 in Fig. 3 may be bonded (as by an epoxyresin) to the longitudinal ends of the core 40, but I illustratesubstantially matched head and tail weights 1516 to show the device foruse as a bidirectional radiator, that is, for like (but opposed)radiation at both longitudinal ends. Extensive-surface bonding isachieved by fitting the wound-core ends in suitable recesses 46-47 inthe head and tail weights 15-16.

Fig. 4 may also be viewed as illustrative of an embodiment of theinvention in which the core 40 is itself permanently magnetized, and theinsert 44 is merely an unpolarized coupler, in order to complete themagnetic flux path. In such event, the material of the permanentlymagnetized core 40 is preferably a nickel ferrite having a relativelysmall addition of cobalt ferrite, while the coupler is preferably amanganese-zinc ferrite.

It will be seen that I have described at basically simpletransducer-element construction and method of construction, featuringeconomy of the use of megnetostrictive material and reducing to aminimum the number of separate handling operations required in theproduction of the assembly. I find that even though the head and tailweights 15-16 (or 15-16) are separately formed and are therefore notintegral with the core 10 (or 40), the bonding at precision-formedcavities 17-18-19 (or 46-47) may be good, hard and permanent so thatefficiency need not be sacrificed.

While I have described the invention in detail for the preferred formsillustrated, it will be understood that modifications may be made Withinthe scope of the invention as defined in the claims which follow.

I claim:

1. In an electromechanical transducer, a substantially continuous andclosed magnetic flux-path core comprising two laterally spaced elongatedlegs of magnetostrictive material joined by an integral yoke at one end,said legs having a width measured in said lateral direction of spacingbetween said legs and a height measured in a direction at right anglesto said width, said legs defining substantially continuousflux-transmitting paths therethrongh over a plurality of planesextending widthwise of said legs from opposing edges of said legsoutwardly for appreciable distances, a magnetic connecting elementformed of magnetic flux conducting material connected between said legsat points along the length remote from said yoke and extending along theheight of said legs for a substantial distance in close flux-conductingadjacency with a plurality of said flux-transmitting planar paths atsaid opposed edges of said legs, means for magnetically polarizing saidcore, winding means linked to said legs, and end counterweights bondedto the respective longitudinal ends of said legs and yoke.

2. The transducer of claim 1, in which said legs and yoke are formedfrom a single block of magnetostrictive material. 1

3. The transducer of claim 2, in which said magnetic connecting elementis permanently magnetized and comprises said magnetic polarizing means.

4. The transducer of claim 2, in which a portion of said leg-yokecombination is permanently magnetized and comprises said magneticpolarizing means.

5. The transducer of claim 2, in which said end counterweights arerecessed, said respective longitudinal ends of said legs and yoke, andat least a portion of said magnetic connecting element, being receivedwithin said recesses.

6. The transducer of claim 2, in which the end counterweight bonded tosaid yoke is relatively light compared to the end counterweight bondedto the other longitudinal end of said legs.

7. The transducer of claim 1, in which said legs and yoke are formedfrom a plurality of laminations planarly oriented in the direction ofand comprising said fluxtransmitting planar paths.

8. The transducer of claim 7, in which said magnetic connecting elementis permanently magnetized and comprises said magnetic polarizing means.

9. The transducer of claim 7, in which a portion of said leg-yokecombination is permanently magnetized and comprises said magneticpolarizing means.

10. The transducer of claim 7, in which said end counterweights arerecessed, said respective longitudinal ends of said legs and yoke, andat least a portion of said magnetic connecting element, being receivedwithin said recesses.

11. The transducer of claim 7, in which the end counterweight bonded tosaid yoke is relatively light compared to the end counterweight bondedto the other lon gitudinal end of said legs.

12. The transducer of claim 1, in which said magnetic connecting elementis parmanently magnetized and com prises said magnetic polarizing means.

13. The transducer of claim 1, in which a portion 01 said leg-yokecombination is permanently magnetized and comprises said magneticpolarizing means.

14. The transducer of claim 1, in which said end counterweights arerecessed, said respective longitudinal ends of said legs and yoke, andat least a portion of said magnetic connecting element, being receivedwithin said recesses.

15. The transducer of claim 1, in which the end counterweight bonded tosaid yoke is relatively light compared to the end counterweight bondedto the other longitudinal end of said legs.

16. In an electromechanical transducer, a continuous and closed magneticflux-pathcore, comprising a consolidated stacked plurality of like flatlaminations of magnetostrictive metal, said laminations being of forkedconfiguration, including two laterally spaced elongated legs of uniformwidth joined by an integral yoke at one end, a permanently magnetizedferrite block bonded to and joining said legs at the other longitudinalend thereof, said ferrite block being of height sufiicient to overlapthe height of said legs, whereby magnetic flux may thread directly anduniformly between said block and the edges of all laminations of saidplurality, winding means linked to the legs of the magnetic circuitdefined by said stacked laminations and by said block, and. recessed endcounterweights fitting the respective longitudinal ends of said legs andyoke and bonded thereto.

17. In an electromechanical transducer, a continuous and closed magneticflux-path core, comprising a consolidated stacked plurality of like flatlaminations of magnetostriotive metal, said laminations including twolaterally spaced elongated legs of uniform width joined by an integralyoke at one end, a permanently magnetized ferrite block bonded to andjoining said legs at the other longitudinal end thereof, said ferriteblock being of height overlapping the combined height of said legs,whereby magnetic flux may thread directly and uniformly between saidblock and the edges of all laminations of said plurality, separate likewindings coupled to the respective longitudinally extending legs of saidstack, and recessed end counterweights fitting the respectivelongitudinal ends of said legs and yoke and bonded thereto. 18. In anelectromechanical transducer, a continuous and closed magnetic flux-pathcore, comprising a consolidated stacked plurality of like flatlaminations of magnetostrictive metal, said laminations including twolaterally spaced elongated legs of uniform width joined by an integralyoke at one end, a permanently magnetized ferrite block bonded to andjoining said legs at the other longitudinal end thereof, said blockoverlapping corresponding parts of the edges of all said laminations,whereby magnetic flux may thread directly and uniformly between saidblock and the edges of all laminations of said plurality, winding meanslinked to the magnetic circuit defined by said stacked laminations andby said block, a recessed head weight of relatively light metal fittingthe yoke end of said core and bonded thereto, and a recessed tail weightof relatively heavy metal fitting the other longitudinal end of saidcore and bonded thereto.

19. A transducer according to claim 18, in which the material of saidhead comprises essentially aluminum. 20. A transducer according to claim18, in which the material of said tail comprises essentially a zincalloy. 21. In an electromechanical transducer, a continuous and closedmagnetic flux-path core, comprising a consolidated stacked plurality oflike fiat laminations of magnetostrictive metal, said laminationsincluding two laterally spaced elongated legs of uniform width joined byan integral yoke at one end, a permanently magnetized ferrite blockbonded to and joining said legs at the other longitudinal end thereof,said block being in close and direct flux-conducting adjacency withcorresponding edge parts of both legs of all laminations, said blockbeing bonded at a location longitudinally short of the other ends ofsaid laminations, whereby the ends of said legs project beyond saidblock, winding means linked to the magnetic circuit defined by saidstacked laminations and by said block, and head and tail weights bondedto the respective longitudinal ends of said stack, said tail weighthaving two separate recesses conforming to the individual cross sectionsof the projecting ends of said legs and receiving said projecting endsand bonded thereto.

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